A battery pack in which many batteries are connected in serial or parallel is used in an electric vehicle or the like. Such a battery pack has a problem in that an output and a rechargeable capacity thereof decrease at low temperature. To address the above, there has been conventionally suggested provision of a heater to a battery pack so as to heat the respective batteries when the temperature is low.
For example, Patent Document 1 discloses a technique for heating a cylindrical battery, using a sheet-like heater, in a battery pack including a plurality of cylindrical batteries and a battery holder wherein battery storage spaces for storing the plurality of cylindrical batteries are individually defined, the sheet-like heater being mounted between the inner surface of the battery storage space and the outer surface of the cylindrical cal battery.
Patent Document 2 discloses a battery pack structure having a plurality of rectangular batteries, a case having a separating part separated from the rectangular batteries, for storing the plurality of rectangular batteries, and a heater mounted on the outer surface of the separating part, and a technique for heating the rectangular batteries via the air present between the separating part and the battery section.
Patent Document 3 discloses a technique for heating a cylindrical battery, using a heater secured on a side surface of a battery holder, in a battery pack including a plurality of cylindrical batteries and a metallic battery holder for holding the plurality of respective cylindrical batteries.